Garden Ponds are a great way to enjoy your California backyard

Fishes For Pond And Aquarium Fishes, living as they do in an element totally different from that in which most other animals live, are difficult to understand. We can appreciate better the outlook of pet birds, say, because they have their being in the familiar air. That is why, partly, the study of fishes is so perplexing, especially in regard to keeping them in captivity.

Nevertheless, we are cognisant of the functions of the fish's principal organs, and given this knowledge the aquarist must, perforce, rely on his own common sense. Fishes do not possess lungs, excepting a few tropical species ; instead they extract oxygen from the water with their branchiae. These consist of six rods of bone situated on each side of the throat, covered with mucous membrane well supplied with blood vessels.

The water is taken in by the mouth and passes over the branchiae and makes its exit at the gill openings. Blood is pumped from the heart to the branchiae, where it is purified, and then distributed to all parts of the creature's body. The process, you will observe, is the reverse to that in human beings. With us it is purified blood that is issued by the heart to the rest of the body ; with the fish the blood is cleansed after leaving the heart. The branchial apparatus of the fish corresponds to our lungs.

The nervous system is not very complicated, neither are there many nerves to trouble the fish, in fact quite large areas are devoid of nerves and there is little doubt that pain, as we know it, is almost unknown to the finny tribe. The surface nerves seem to be concentrated to one line on each side of the body, forming the lateral line. This is not very prominent in the ordinary goldfish, but in other species can be seen as a dark line running from the gills to the tail, approximately along the middle of the fish. The function of this line of nerves is that of receiving vibrations, in other words it acts as a kind of auxiliary ear.

The Carp family are peculiar in having no teeth in their mouth ; the masticating apparatus is situated in the throat and consists of two irregularly shaped bones and, in reality, the food is eaten after it is swallowed. Other fishes, especially those of carnivorous habits, may have teeth on the upper and lower jaws, the tongue-this, by the way, is immovable-and the roof of the mouth.

From the branchial arches in the mouth of most fishes hang comb-like fringes and these serve as sieves. As the water passes through the mouth to the gill openings many minute organisms are retained by these ' gill-rakers ' and so the fish receives an addition to its diet. The alimentary system differs very little from that of the higher animals.